ELECTRIC MOTORS An Introduction to DC and Stepper Motors

Electric Motors Electric motors are everywhere! In your house, almost every mechanical movement that you see around you is caused by an AC or DC electric motor.

Direct Current Motors overall plan of a simple 2- pole DC electric motor A simple motor has 6 parts, as shown in the diagram

Direct Current Motors

Brushed DC Motor The brushed DC motor is one of the earliest electric motor designs Easy to understand design Easy to control speed

DC STEPPER MOTORS Stepping motors are electric motors without commutators Commutation is handled externally by the motor controller Controller charges opposite coils attracting the center rotor magnets

DC STEPPER MOTORS

Voltage Rating –provides desired torque Resistance-per-winding determines –the current draw of the motor –Maximum operating speed Degrees per Step –Sets the number of degrees the shaft will rotate for each full step

UNIPOLAR STEPPER MOTOR Relatively easy to control simple 1-of-'n' counter circuit can generate the proper stepping sequence 1 transistor per winding

UNIPOLAR STEPPER MOTOR two center-tapped coils represents the connection of a 4 - phase unipolar stepper motor

UNIPOLAR STEPPER MOTOR 6 wires with a center tap on each of two coils

IDENTIFYING WIRES Check make and model to see if wire colour code is availableCheck make and model to see if wire colour code is available Observe the wires to see if you can identify groups of 3 wiresObserve the wires to see if you can identify groups of 3 wires Measure resistance between wiresMeasure resistance between wires Wire with lowest resistance is power wireWire with lowest resistance is power wire

IDENTIFYING WIRES 6 wire motors –Groups of 3 wires –1 power & 2 signal 5 wire motors –1 power & 4 signal wires power wire has lowest resistance to the otherspower wire has lowest resistance to the others

CONTROL PROGRAM Once wires identified and connected to the circuit: a program is needed to run the motor Example Turing Program: loop parallelput (1) delay (500) parallelput (2) delay (500) parallelput (4) delay (500) parallelput (8) delay (500) end loop

STEPPER MOTOR CONTROL 4 signal wires fired in the correct sequence will turn the motor